Preparation of dimethyl hydrazine



United States Patent @fifice 3350,5 Patented Aug. 21, 19%2 3 see PREPARA'HON or ionrn'rrrrr. HYDRAZKNE Carl L. Randolph, J12, Whittier, and Ralph E. Meyer,

It may also be observed that the presence of alkali does not significantly affect the yield.

The corresponding bromo and iodo derivatives may be used in the practise of this invention in place of dialkylchloramines.

tion temperature does not appear to be critical so long as it is above 0 C.

' m n I 5 2:2 l izi j aifi irgiifi o iiis 5 252 Camera The reaction may also be conducted in the vapor N0 Drawing Filed 15 1954, sel. Nun 410,412 phase as well as in aqueous solution at a prl above 7;

6 Claimg. (CL 250.433 the only critical limitation being temperature. Liquid ammonia is a readily available commercial This invention relates to a new method of preparing 10 item. The halo amines used as starting materials, alunsymmetrical dialkyl hydrazines and in particular to a though not presently available on a tonnage basis can method for preparing dimethyl hydrazine. be prepared in large quantities at extremely low cost.

Hydrazine for many years has found extensive use as Dimethyl chloramine by Way of illustration can be prea rocket fuel because of its high specific impulse. Unpared by the action of aqueous sodium hypochlorite solufortunately, however, hydrazine has a freezing point tion upon dimethyl amine hydrochloride or even more of about 33 F. making it necessary to add freezing point economically from alkali, chlorine and dimethylamine depressants to permit its use as a rocket fuel under ordiail of which are cheap and readily available. nary operating conditions. However, it has been ob- .In view of the commercial availability of the starting served that such additives also depress the specific immaterials used in this process as well as the ease in repulse of the fuel thereby decreasing the efiiciency of the covering the final product, it is at once apparent that englne' this method will have wide applicability for industrial It has now been found that dimethyl hydrazine has production of unsymmetrical dialkyl hydrazines. a specific impulse approximating that of hydrazine and Although slight reductions in yield may be predicted a freezing point of -70 F. thereby permitting its use by the increase in chain length of the alkyl component, as a rocket fuel Without additives. g5 nevertheless it is apparent that this method can be em- Although dimethylhydrazine was first prepared as early ployed to synthesize the higher homologues of dimethyl as 1875, there have been no methods heretofore availahydrazine as well. ble which would permit its production on a commercial We claim: scale, and hence its use as a rocket fuel has been severely 1. The method of preparing unsymmetrical lower direstricted. alkyl hydrazine hydrohalide which comprises reacting a By the practice of this invention dialkyl hydrazine; lower dialkyl halo amine with ammonia at a temperacan be produced on a tonnage basis, utilizing cheap, ture above about 0 C. readily available, starting materials with a minimum of 2. The method of preparing unsymmetrical dimethyl handling, thereby making the use of dirnethyl hydrazine hydrazine hydrochloride which comprises reacting dias a rocket fuel an economic possibility. We have found methyl ohloramine with ammonia at a temperature above that alkyl chloramines will react with liquid ammonia about 0 C. at room temperature to yield dialkyl hydrazines in ac- '5. The method of preparing unsymmetrical dimethyl cordance with the general reaction scheme set forth behydrazine hydrochloride which comprises reacting dilow, wherein R is a lower alkyl radical: methyl chloramine with liquid ammonia in a sealed ves- 40 sel at a temperature above about 0 C. R2NC1+NH3 )R2N NH2'HC1 4. The method of preparing unsymmetrical dirnethyl In order to determine optimum reaction conditions hydrazine hydrochloride which comprises reacting difor this procedure, a series of experiments was performed methyl chloramine with liquid ammonia at a temperature under various conditions. In order to illustrate more of about 20 C. clearly this invention the results of these experiments are 5 T method of Preparing unsymmfitlical lower submitted in tabular form below. The reactions were alkyl hydrazines which comprises reacting a lower di- E Percent a are an as ee Hydrazine 5.0 1.0 unknown 0 0 5.0 1.0 130 (approx.) 20 30.5 5.0 0.0 130 (approx.) 20 21.5 5.0 1.0 130 (approx). 20 22.5 5.0 0.0 130 (approx.). 20 26.7 5.0 1.0 130 (approx.) 20 22.5 5.0 1.0 130 (approx.). 20 27.5 5.0 0.0 130 (approx.) 20 24.7 90 mm 5.0 1.0 230 105 20.0

all conducted in sealed ampoules under the conditions alkyl halo amine with ammonia at a temperature above set forth in the table. Dimethyl chloramine was weighed about 0 C. in the presence of potassium hydroxide.

into the amopules and subsequently liquid anhydrous am- 6. The method of preparing unsymmetrical dirnethyl monia was distilled in. The ampoules were then sealed, hydrazine which comprises reacting dimethyl chloramine warmed to the reaction temperature and allowed to with ammonia at a temperature above about 0 C. in the stand for the indicated time. After opening the tubes, presence of potassium hydroxide. the ammonia was vaporized and the white solid residue of dimethyl hydrazine hydrochloride was dissolved in References Cited in the file of this Patent water and titrated with potassium iodate to determine UNITED STATES PATENTS the yleld- 2,808,439 Barrett a a1. Oct. 11, 1957 As may be seen from the results given above the reac- OTHER REFERENCES Westphal: Berichte, 74B (1941), pages 759, 760. 

1. THE METHOD OF PREPARING UNSYMMETRICAL LOWER DIALKYL HYRAZINE HYDROHALIDE WHICH COMPRISES REACTING A LOWER DIALKYL HALO AMINE WITH AMMONIA AT A TEMPERATURE ABOVE ABOUT 0*C. 